Cutting insert

Abstract

A cutting insert is disclosed which includes a polygonal plate-like insert body defined by a front face, a rear face and a plurality of side faces lying between the front face and the rear face. The insert body has at least one main cutting edge defined by the intersection of the front face with one of the side faces and at least one nose portion intersecting the at least one main cutting edge and defined by one of the corners of the front face. The front face has an inclined surface extending immediately from the nose portion and sloping toward the rear face in a direction away from the nose portion.

What is claimed is: 
     
       1. A cutting insert comprising: a tetragonal plate-like insert body defined by a front face, a flat rear face and two opposite pairs of side faces disposed between said front face and said rear face, said insert body including: a pair of generally straight main cutting edges defined by the intersections of said front face with one opposite pair of said side faces,   a pair of auxiliary cutting edges defined by the intersections of said front face with the other opposite pair of said side faces, and   a pair of nose portions defined by an opposite pair of corners of said front face, each nose portion being disposed between a respective main cutting edge and a respective auxiliary cutting edge so as to intersect therewith, said front face having a pair of inclined surfaces each extending immediately from a respective nose portion and sloping toward said rear face in a direction toward a diagonal line of the front face which connects the corners of the front face other than the corners defining said nose portions.     
     
     
       2. A cutting insert as recited in claim 1, wherein said pair of inclined surfaces are directly joined to each other. 
     
     
       3. A cutting insert as recited in claim 1, wherein said front face is defined by said pair of inclined surfaces and a flat surface disposed between said inclined surfaces. 
     
     
       4. A cutting insert as recited in claim 2, wherein said insert body is of a parallelogrammic shape having two acute corners with an angle of between 70° and 85°, said inclined surface having an inclination angle ranging from 3° to 20°, the intersection defining said main cutting edge having an inclination angle ranging from 3° to 15°, said intersection defining said auxiliary cutting edge having an inclination angle ranging from 3° to 20°. 
     
     
       5. A cutting insert as recited in claim 1, wherein the other opposite pair of said side faces are concavely formed as viewed from said front face. 
     
     
       6. A cutting insert comprising: a tetragonal plate-like insert body defined by a front face, a rear face and two opposite pairs of side faces disposed between said front face and said rear face, said insert body including: a pair of main cutting edges defined by the intersections of said front face with one opposite pair of said side faces,   a pair of auxiliary cutting edges defined by the intersections of said front face with the other opposite pair of said side faces, and   a pair of nose portions defined by an opposite pair of corners of said front face, each nose portion being disposed between a respective main cutting edge and a respective auxiliary cutting edge so as to intersect therewith, said front face having a pair of inclined surfaces each extending immediately from a respective nose portion and sloping toward said rear face in a direction toward a diagonal line of the front face which connects the corners of the front face other than the corners defining said nose portions, the other opposite pair of said side faces being concavely formed as viewed from said front face.